Engineered viral systems present great opportunities for therapeutic applications. The genomes of many viruses have been sequenced and characterized with respect the replication, packaging, immune evasion, protective antigens, killer toxin, immunity proteins, etc. Utilizing this information, viruses have been altered for use as attenuated vaccines or engineered for use as protein expression systems for use in gene therapy, vaccines and protein products. Examples of viruses that have been used in this manner include alphaviruses, adenoviruses, baculoviruses, pox viruses, rhabdoviruses, picornaviruses, noroviruses, niedoviruses, nidoviruses, and flaviviruses.
As described above, viral systems have been effectively used as vaccines, primarily based on protein expression and presentation to the immune system. It has recently been discovered that dsRNA specific to genetic sequences can control or prevent gene expression. This has broad utility for products in agriculture, aquaculture, veterinary and human therapeutics and vaccines. To date the delivery of dsRNA has been primarily accomplished by technologies that artificially associate dsRNA in particles using lipids, polymers, and recombinant proteins mixed with other molecules like cholesterol and targeting ligands. In addition to these in vitro particulate approaches, direct conjugates of dsRNA to targeting ligands are also being developed. Furthermore dsRNA has been delivered through recombinant plant and E. coli material, direct injection, oral exposure, electroporation or immersion of purified dsRNA. However, each of these systems has significant limitations in efficacy, consistency, toxicity, delivery, stability, cost-of goods, manufacturing feasibility etc. This is further illustrated by the fact that there are no licensed products on the market for human, animal or insect applications.
It would therefore be advantageous to be able to engineer and utilize dsRNA viruses naturally found in a wide variety of yeast or fungi to deliver and/or propagate a recombinant dsRNA molecule in a virus or particle, which could be introduced into an organism to be treated to regulate gene expression in the organism or in a pathogen infecting the organism. With such compositions and methods, a highly useful system for efficient production and delivery of packaged dsRNA could be achieved.